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I hope someone will be able to help me with this.

We have recently migrated all of our clients' sites to a new server running IIS7 - all the sites were originally running on a server running IIS6.

Ever since the migration, lots of our clients are reporting error messages. There seems to be quite a number of issues related to sending emails and also, we have had the following error message reported by several different clients:

    Server Error in '/' Application.
--------------------------------------------------------------------------------

Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Web.HttpException: Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.

I have read elsewhere that this error can appear if a button is clicked before the whole page has finished loading. But as this error has now appeared on multiple sites and only since the server migration, it seems to me that it must be something else.

I was wondering if someone could tell me if there is something specific which needs to be changed for .NET sites when sites are moved from a server running IIS6 to a server running IIS7? I don't deal with the actual servers very much so I'm afraid this is very much a grey area for me.

Any help would be very much appreciated.

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What version of .net are the servers running? Do you have a full stack trace from any of your customers? Do you have corresponding Event Log Entries. Machine Validation issues can come from a number of places. Did the physical setup of the machines change? For example did any of the sites previously run on a single server but now they are on multiple and load balanced? –  Dave Holland Nov 13 '10 at 3:21
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2 Answers 2

It sounds like you migrated the sites without actually doing any research regarding what needed to be done, what dependencies existed, etc., etc. It also sounds like you don't have a very good handle on the platform the client sites are running on. The client sites are running on .NET and you don't know what needs to be done to run a .NET site on IIS 7? My recommendation would be to migrate the client sites back to IIS 6 until you've done your homework on IIS 7.

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Thank you for your response - I didn't actually do the migration myself as I don't deal with the server set up etc. But as the migration has been carried out and we are receiving .NET errors, I have been asked to look into why it is happening. I appreciate that I don't have much server knowledge at all, which is why I am trying to ask what the dependencies are. If you would have any helpful advice on this it would be appreciated. –  Leah Nov 12 '10 at 15:16
    
There's a lot of info coming back from a google search, I don't know how much of it will be helpful to you. Here are a couple links: learn.iis.net/page.aspx/427/…. blogs.iis.net/bills/archive/2008/06/18/…. learn.iis.net/page.aspx/110/…. –  joeqwerty Nov 12 '10 at 19:15
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There are couple of articles link 1 and link 2 that can help you understand the issue and resolve it.

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Thank you for your help. I've had a read through both articles but do you think that migrating the sites to the new server would be the cause either of these? NET 3.5 SP1 was already installed on the old server I believe, so I would have thought that we would have already received these errors wouldn't we? Also, for the second link, if it was an issue with the page not being fully loaded, could that not have happened on the old server too? It could be a huge coincidence I suppose that we are getting the errors just after the migration, but just seems a bit strange. Thanks again for your help. –  Leah Nov 12 '10 at 15:25
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